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Commit fa3f82c8 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
Browse files

powerpc/smp: soft-replugged CPUs must go back to start_secondary 



Various thing are torn down when a CPU is hot-unplugged. That CPU
is expected to go back to start_secondary when re-plugged to re
initialize everything, such as clock sources, maps, ...

Some implementations just return from cpu_die() callback
in the idle loop when the CPU is "re-plugged". This is not enough.

We fix it using a little asm trampoline which resets the stack
and calls back into start_secondary as if we were all fresh from
boot. The trampoline already existed on ppc64, but we add it for
ppc32

Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 963e5d3b

arch/powerpc/include/asm/smp.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -36,6 +36,7 @@ extern void cpu_die(void); 




extern void smp_send_debugger_break(int cpu);

extern void smp_send_debugger_break(int cpu);

extern void smp_message_recv(int);

extern void smp_message_recv(int);

extern void start_secondary_resume(void);





DECLARE_PER_CPU(unsigned int, cpu_pvr);

DECLARE_PER_CPU(unsigned int, cpu_pvr);

arch/powerpc/kernel/head_32.S

+9 −0
Original line number Original line Diff line number Diff line
@@ -890,6 +890,15 @@ __secondary_start: 
	mtspr	SPRN_SRR1,r4

	mtspr	SPRN_SRR1,r4

	SYNC

	SYNC

	RFI

	RFI



_GLOBAL(start_secondary_resume)

	/* Reset stack */

	rlwinm	r1,r1,0,0,(31-THREAD_SHIFT)	/* current_thread_info() */

	addi	r1,r1,THREAD_SIZE-STACK_FRAME_OVERHEAD

	li	r3,0

	std	r3,0(r1)		/* Zero the stack frame pointer	*/

	bl	start_secondary

	b	.

#endif /* CONFIG_SMP */

#endif /* CONFIG_SMP */





#ifdef CONFIG_KVM_BOOK3S_HANDLER

#ifdef CONFIG_KVM_BOOK3S_HANDLER

arch/powerpc/kernel/smp.c

+7 −2
Original line number Original line Diff line number Diff line
@@ -502,7 +502,7 @@ static struct device_node *cpu_to_l2cache(int cpu) 
}

}





/* Activate a secondary processor. */

/* Activate a secondary processor. */

int __devinit start_secondary(void *unused)

void __devinit start_secondary(void *unused)

{

{

	unsigned int cpu = smp_processor_id();

	unsigned int cpu = smp_processor_id();

	struct device_node *l2_cache;

	struct device_node *l2_cache;
@@ -558,7 +558,8 @@ int __devinit start_secondary(void *unused) 
	local_irq_enable();

	local_irq_enable();





	cpu_idle();

	cpu_idle();

	return 0;



	BUG();

}

}





int setup_profiling_timer(unsigned int multiplier)

int setup_profiling_timer(unsigned int multiplier)
@@ -660,5 +661,9 @@ void cpu_die(void) 
{

{

	if (ppc_md.cpu_die)

	if (ppc_md.cpu_die)

		ppc_md.cpu_die();

		ppc_md.cpu_die();



	/* If we return, we re-enter start_secondary */

	start_secondary_resume();

}

}



#endif
 
#endif

arch/powerpc/platforms/pseries/offline_states.h

+0 −2
Original line number Original line Diff line number Diff line
@@ -34,6 +34,4 @@ static inline void set_default_offline_state(int cpu) 
#endif

#endif





extern enum cpu_state_vals get_preferred_offline_state(int cpu);

extern enum cpu_state_vals get_preferred_offline_state(int cpu);

extern int start_secondary(void);

extern void start_secondary_resume(void);

#endif
 
#endif